The present invention relates to a device for a Polymerase Chain Reaction (PCR) and, more particularly, to a device that can be used in conjunction with a handheld instrument to detect the presence or absence of a biological agent in a sample using PCR technology.
PCR technology can be used by facility security professionals, military forces, and first responders, such as fire fighters, police, emergency medical personnel, and HAZMAT teams, to determine whether a life threatening biohazard is present at locations on-site and in the field. For example, a biological detection instrument utilizing PCR technlology can be used to test a sample for the presence of a biological agent, such as anthrax, providing accurate results in forty minutes or less.
The sample is first formulated into a PCR reaction mixture in a disposable reaction tube. The reaction tube is inserted into a chamber in a reaction device in the instrument. In the reaction device, the reaction mixture undergoes thermal cycling (heating and cooling). The presence or absence of the biological agent is optically detected by the instrument.
One disadvantage of conventional reaction devices is that such reaction devices are too heavy and complex to be packaged into a portable (handheld) biological detection instrument that is suitable for use on-site and in the field. For example, a conventional reaction device consists of a metal block through which heating and cooling fluids are passed to heat and cool the reaction mixture (see, e.g., U.S. Pat. No. 5,555,675, incorporated by reference herein). The metal block and the components necessary for controlling fluid temperature and supply increase the weight and complexity of the reaction device. As a result, the weight and complexity of the biological detection instrument increases so that the instrument can not be easily transported to on-site and field locations.
Another disadvantage of conventional reaction devices is that such reaction devices can not heat and cool the reaction mixture rapidly or efficiently. For example, the metal block of a conventional reaction device has a high coefficient of thermal conductivity so that heat is conducted away from the reaction mixture through the metal block back into the instrument. Thus, the heating efficiency of the reaction device is reduced. As a result, a time period for completing a thermal cycle is increased.
Although some conventional reaction devices employ micro-machined silicon with an integrated heating element to rapidly heat and cool the reaction mixture, such reaction devices suffer from relatively high tooling, labor, and production costs (see, e.g., U.S. Pat. No. 5,589,136, incorporated by reference herein). Additionally, the fragility of micro-machined heaters makes such heaters impractical for portable field use.